Authors:

Publish Date: 2008

Volume:, Issue:, Pages: 165-180

Abstract

Soil is the largest reservoirs of carbon, accounting for 2011 GtC, or 81% of the total carbon in the terrestrial biosphere (WBGU 1998). Flow of carbon between soil and the atmosphere is a continuous process, highly influenced by land use and management (Paustian et al. 1997). Organic carbon stored in soil is an important carbon pool for many land-use systems and projects, and even for national greenhouse gas inventories of different land-use categories. “Soil organic carbon” is also often referred to as “soil organic matter”. Soil organic matter includes the whole non-mineral fraction of soil ranging from decayed plant and animal matter to brown to black material that bears no trace of the original anatomical structure of the material and is normally defined as “soil humus”. Soil organic matter also includes living and dead microbial tissue, compounds synthesized by microorganisms and derivatives of these materials produced as a result of microbial decay. Soil organic carbon as defined by IPCC (2006) comprises “organic carbon in mineral soils to a specific depth chosen, also including live and dead fine roots within the soil”. Although both organic and inorganic forms of carbon are found in soil, land use and management typically has a larger impact on the stocks of organic carbon. Therefore, this chapter focuses on soil organic carbon. Further, soil organic carbon is relevant to both mineral and organic soils. Organic soils contain a minimum of 12– 20% organic matter by mass and are found under poorly drained conditions of wetlands (Brady and Weil 1999). All other soils are classified as mineral soils, which typically have relatively low amounts of organic matter. Mineral soils dominate most ecosystems except wetlands and are the focus of this chapter.